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Which programmer for CM927 RF roomstat?
- Thread starter jblack
- Start date
The CM927RF is a combined programmer and room stat, but it only controls the heating side. You need a second cheap single channel time clock to control the HW side. It does not have to be fancy as it will be set when you install it (HW on 0600-0800 then 1800 to 2300 for example) and then forgotten. An override facility, for when you run out of hot water, is useful.
Read Honeywell User Guide for S Plan with Programmable Thermostat
The matching prog for the CMT927 is the ST9400C (two channel).
I think the one channel version is the ST9100 but we only fit the 9400C so I'm not sure. Both use the same LoT programming scheme as the CMT927, and share similar looks.
I think the one channel version is the ST9100 but we only fit the 9400C so I'm not sure. Both use the same LoT programming scheme as the CMT927, and share similar looks.
Simond, I've just fitted a CM927 to my system that has an ST6400C programmer. Two questions I'd like to ask:
1 - If I keep the ST6400 how do I set the heating side?
2 - Or should I replace it with an ST9400C ?
Thanks.
1 - If I keep the ST6400 how do I set the heating side?
2 - Or should I replace it with an ST9400C ?
Thanks.
There is no need to replace the ST6400
Terminal 4 on the ST6400C is the CH on terminal, so you should disconnect the lead from this terminal and at the other end. Make the wire safe by cutting off the bare wires at each end. Then wire the CM927 as per its wiring diagram.
The ST6400C will then act just as an HW timer
Thanks for the prompt reply. In the meantime I've had the following diagram sent from Honeywell technical support, the number 4 connection on the programmer is shown connected! Any comments? It also happens to be the way I have my system setup at present.
Can I assume that if I leave it like the diagram then I must set my ST6400C to continuous on the heating side and that the CM927 will then control the heating?
Honeywell did not send me any instructions!
Honeywell did not send me any instructions!
Wiring as shown in the Honeywell diagram will work OK, provided you leave the CH switch on continuous/24hr. The only problem is that there are now two switches controlling the CH, the one on the ST6400C and the one on the CM927. If the ST6400C is accidentally turned off ...
Completely disabling the CH side on the ST6400C is, I suggest, a better way of doing it. In this case you will need to provide a link between L and A on the CM927.
What if you have two heating zones, or three? It seems odd that the zone with a CM927 cannot be turned off by the programmer. My heating program is on 24 hours a day because all zones are programmable (but not wireless), but if I go away the programmer can turn off all the heating at once.
I want to add a wireless zone, but it seems that I cannot simply replace an existing controller because they are not wired with a permanent live. Is this correct? I only want the live to go off when I am on holiday.
I want to add a wireless zone, but it seems that I cannot simply replace an existing controller because they are not wired with a permanent live. Is this correct? I only want the live to go off when I am on holiday.
You could change the wiring so that each prog stat was not fed via the programmer CH channel and permanently fed with a live. This would allow you to fit your mains receiver in direct place of a standard wired stat.
But this would remove the ability to drop all heating from the CH programmer.
Surely, if you are going to fit a wireless stat, why don't you fit the receiver next to the wiring centre? I assume the range would be OK. In this position you would easily pick up all the cables you need. Just blank off the old stat.
But this would remove the ability to drop all heating from the CH programmer.
Surely, if you are going to fit a wireless stat, why don't you fit the receiver next to the wiring centre? I assume the range would be OK. In this position you would easily pick up all the cables you need. Just blank off the old stat.
simond, you are a genius 
. Funny how you don't change your thinking when a new technology like wireless comes along.
. Funny how you don't change your thinking when a new technology like wireless comes along.I am thinking of replacing a Honeywell T6360B with the 927.
I also have a ST6400C controlling the hot water and heating at present, with a separate Nu-Heat prgrammable stat controlling the underfloor heating in the kitchen.
If I want to leave the ST6400C with the CH set at constant (as suggested by Honeywell technical support) what connections do I need to make on the 927?
The T6360B has yellow -> 3, blue -> 2 and red -> 1 as well as an earth connection.
I think I need to connect red -> L, blue -> N and yellow -> B and there would be no need to link L -> A. Is this correct?
After reading this thread I did look in the wiring box and was surprised at how much there was in there and unfortunately none of it is labelled
There is hardly any room in the airing cupboard to put the 927's receiver so I am inclined to simply replace the existing stat on the hall wall.
My boiler is a Vokera Eclipse ESS. Do any of the settings need to be changed on this e.g. the anti cycle time - from what I have read elsewhere the 927 is likely to cause the boiler to go on and off frequently as the stat gets near the desired temperature which would suggest a very low anti cycle time is required.
I also have a ST6400C controlling the hot water and heating at present, with a separate Nu-Heat prgrammable stat controlling the underfloor heating in the kitchen.
If I want to leave the ST6400C with the CH set at constant (as suggested by Honeywell technical support) what connections do I need to make on the 927?
The T6360B has yellow -> 3, blue -> 2 and red -> 1 as well as an earth connection.
I think I need to connect red -> L, blue -> N and yellow -> B and there would be no need to link L -> A. Is this correct?
After reading this thread I did look in the wiring box and was surprised at how much there was in there and unfortunately none of it is labelled
There is hardly any room in the airing cupboard to put the 927's receiver so I am inclined to simply replace the existing stat on the hall wall.
My boiler is a Vokera Eclipse ESS. Do any of the settings need to be changed on this e.g. the anti cycle time - from what I have read elsewhere the 927 is likely to cause the boiler to go on and off frequently as the stat gets near the desired temperature which would suggest a very low anti cycle time is required.
If you want to retain the ability of the ST6400C to turn off all CH then you do not have enough wires in the T6360.
It is far better to wire from the wiring centre, I suggest if you are not up to it find an electrician or a wiring conversant heating installer. You seriously weren't expecting the wiring centre to be labelled up for a DIY visit ten years later!
You will need to link the permanent live to A in the receiver if you are going to bypass the programmer.
Your colour coding is immaterial, it is what is actually connected that matters. Many a plumber has blown things up relying on colour coding by a previous installer. Don't allow the actual cable colour to convince you of anything.
The 927 has some switching lag variables in the installer menu.
It is far better to wire from the wiring centre, I suggest if you are not up to it find an electrician or a wiring conversant heating installer. You seriously weren't expecting the wiring centre to be labelled up for a DIY visit ten years later!
You will need to link the permanent live to A in the receiver if you are going to bypass the programmer.
Your colour coding is immaterial, it is what is actually connected that matters. Many a plumber has blown things up relying on colour coding by a previous installer. Don't allow the actual cable colour to convince you of anything.
The 927 has some switching lag variables in the installer menu.
why if you already have room stat do you want a wireless version if you intend to put the new stat inthe same position?
If you are then use a cm907 and alter the wiring so that you connect A to 1 and B to 5. Saves you about £40 this will disable the heating channel from the programmer and allow the honeywell cm907 to control on it's own. if you want to use a wireless version then still wire up A to1 and B to 5 . If you want go to the following for latest honeywell wiring guide 14.http://www.honeywelluk.com/download.aspx
If you are then use a cm907 and alter the wiring so that you connect A to 1 and B to 5. Saves you about £40 this will disable the heating channel from the programmer and allow the honeywell cm907 to control on it's own. if you want to use a wireless version then still wire up A to1 and B to 5 . If you want go to the following for latest honeywell wiring guide 14.http://www.honeywelluk.com/download.aspx
I only want the receiver unit in the same place as the existing stat.
The wireless part of the stat that senses the temperature will be located elsewhere (in a room where I am interested in the temperature rather than in the hall).
The wireless part of the stat that senses the temperature will be located elsewhere (in a room where I am interested in the temperature rather than in the hall).
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